I'm planning to use the ADM7170 as 1.2 V voltage source. According to the datasheet ordering guide table (page 23/23), the adjustable models (ADM7170ACPZ-R7 & ADM7170ACPZ-R2) are listed with an output voltage of 1.2 V.
As stated on page 16, every fixed version can be used as an adjustable one. So the "adjustable" model is the fixed one with 1.2 V, by connecting the SENSE pin direct to Vout and Do Not Install R2?
I'm little bit condused by the notation, as it seems every version is an adjustable one, and the "adjustable" one (ADM7170ACPZ-R7 & ADM7170ACPZ-R2) is the fixed one with 1.2V.
To sum it up, the models ADM7170ACPZ-R7 & ADM7170ACPZ-R2 are the fixed version with 1.2 V. Is that correct?
Is there any difference between the fixed models (1.3 V to 5 V) compared to the "adjustable" operated as 1.2 V source, by means of noise performence?
You are right that the VOUT of both the fixed version and adjustable version can be adjusted to a higher voltage. The difference of the fixed and adjustable version is that the adjustable version LDO circuit can be modified to reduce the output voltage noise as shown below:
The models ADM7170ACPZ-R7 & ADM7170ACPZ-R2 are adjustable versions in which you can apply a noise reduction network.
The noise performance of the fixed version if operated at its default output voltage (with no adjust resistors) is 5uVrms. However, when the output voltage is adjusted, noise increases proportional to the output voltage. Only for adjustable models that the noise performance can be reduced as shown above.